1. Field of the Invention
The present invention relates to a positive resist composition.
This application claims priority on Japanese Patent Application No. 2004-98183 filed in Japan, on Mar. 30, 2004, the disclosure of which is incorporated by reference herein.
2. Description of the Related Art
In the production of semiconductor devices and liquid crystal display devices, fine working has rapidly been developed, recently, with the progress of a lithography technique. A light source having a shorter wavelength is generally employed for fine working. Specifically, ultraviolet rays typified by g-rays and i-rays have conventionally been used, but now KrF excimer lasers (248 nm) and ArF excimer lasers (193 nm) have been introduced.
As one of the resist materials which satisfy the conditions of high definition capable of reproducing a pattern having a fine size, for example, there is known a chemically amplified resist composition comprising a base resin and an acid generator generating an acid under exposure, wherein alkali solubility changes due to an action of an acid generated from the acid generator.
As the base resin component of the chemically amplified resist, for example, there can be used polyhydroxystyrene having high transparency to a KrF excimer laser (248 nm), or those wherein a portion of hydroxyl groups are protected with an acid dissociable dissolution inhibiting group.
As the acid generator, for example, onium salt-based acid generators are now used most popularly. Among these acid generators, an onium salt-based acid generator wherein the anion moiety (acid) is a fluoroalkyl sulfonate ion containing an alkyl chain having 1 carbon atom (hereinafter referred to as “C1PAG”) is mainly used and the other acid is not used popularly because of its low acid strength (see, for example, Patent Document 1).
[Patent Document 1] Japanese Patent Application, First Publication No. 2001-51422
However, a resist composition containing C1PAG has the problem that it is inferior in mask linearity (reproducibility of the mask). Therefore, when an Iso line pattern and a line-and-space (L&S) pattern are formed by using a mask having the same line width, the Iso line pattern has a line width smaller than that of the L&S pattern, thus causing a problem such as poor Iso/Dense balance wherein the (Iso) pattern and the (Dense) pattern differ in reproducibility of the mask.